The original DFX inserts were on the firmer side - if I remember correctly, Callaway/Odyssey received feedback from some players that the White Hot insert was too soft, so they provided a firmer option. As you say, though, that doesn't seem to be the case with the current versions - Callaway's description is 'our softest insert technology ever'...
I don't know much about Rife putters, but a couple of other options to consider at the lower-priced end of the market are Wilson and Cleveland - both have milled face offerings in a variety of head shapes (Wilson Infinite, and there have been several Cleveland Huntington Beach series of putters) that get pretty good reviews. I've used putters from both brands (a few rounds with a Wilson Infinite West Loop, and had a Huntington Beach Soft 11 in my bag for several months), and was pretty happy with the feel and performance.